PC-Progress Discussion Forums

From your input I can see that you use either the Kosugi (Model=3) or Durner dual-porosity (Model=5) models. Durner model is obviously not based on the Kosugi's model, but on the van Genuchten-Mualem model. Thus, if you want to compare these two simulations, you need to use consistent models.

J.

It very likely will. Why wouldn't you simply test it yourself? J.

You need to use the keyword "charge", which will indicate the code, which species to adjust to get charge balance. J. SOLUTION 1 pH 7 charge Cl 0.01 Na 1 SOLUTION 2 Cl 1.3 charge Na 2 In the first example, pH of this solution will be adapted to obtain charge balance => pH = 10.98. In the second exam...

I think that these are acceptable mass balance errors. I usually want from the simulation to have the mass balance error for water flow less than 1% (which you have almost 10 times smaller) and for solute transport less than 2-3% (which you also have). You can likely lower the mass balance errors ev...

The best way to learn HYDRUS-1D is with the CSIRO Tutorial eBook: Rassam, D., J. Šimůnek, D. Mallants, and M. Th. van Genuchten, The HYDRUS-1D Software Package for Simulating the Movement of Water, Heat, and Multiple Solutes in Variably Saturated Media: Tutorial, Version 1.00, CSIRO Land and Water, ...

There is an easy way to export x-z coordinates of isolines. 1. First, you need to switch the View to display Isolines: Options->Scalar Field Display->Isolines 2. Then, you use the command Export Isolines (File->Export->Export Isolines). The program than creates a text file "Project_Name_Isolines.txt...

Let me quote from the help: "Free Drainage Water Flow Boundary Condition: A zero-gradient boundary condition can be used to simulate a freely draining soil profile. Such a situation often occurs in field studies of water flow and drainage in the vadose zone. This lower boundary condition is most app...

The pressure head BC, with the pressure head at the bottom of the domain. J.

I would not care that much about streamlines (and velocities) since that is simply postprocessing of results by GUI. I would care more about the calculated pressure heads and boundary fluxes, which are a direct result of calculations. J.

As I wrote above you need to test different grids, with such a large grid anisotropy. You should look at the mass balance errors and accept results that gives you good mass balance errors. J.

Since the pressure head isolines in your problem are likely horizontal, you should use an anisotropic FE mesh. For such conditions you can easily use an anisotropy ratio of the mesh of 1:10, 1:100, or even more. You need to test it. Also, note that you need to have finer discretization only in the u...

HYDRUS provides a graph of Soil Water Storage for the entire profile, as well as Soil Water Storage for different Subregions at Print Times in the Mass Balance Information output. J.

All reported values by HYDRUS related to water content and water storage are in volumetric units, i.e., [cm^3/cm^3] or [cm]. J.

I have found out where the problem was. If I decrease the precision criteria used in the matrix solver (ORTHOMIN), I will avoid these mass balance error problems. Please download the attached computational modules and copy them into the BIN folder, in which HYDRUS is installed (e.g., …. HYDRUS3D 3.0...

You likely have problems exactly because you changed the default parameters. The minimum allowed time step clearly should be smaller or equal to the initial time step, and it should be on the order of 1 s, certainly not 0.5 days. Specifying any value other than zero for the bottom flux is almost alw...